1. Field of the Invention
The present invention relates to a combination ultrafilter/static eliminator adapted for use in a gas blow-off gun for clean room applications.
2. Discussion of the Related Art
Currently, many different types of clean room particle removal devices are commercially available. One type that has proven particularly successful is the so-called gas blow-off gun, such as the "Black Jack", commercially available from Omega Specialty Instrument Co., Chelmsford, MA. These guns include a handle portion connected to a source of gas. A trigger and valve assembly is disposed in the handle portion to control the release of gas into the remainder of the gun. From the handle portion, the gas flows into a cellulose filter cartridge which is surrounded by an outer nozzle housing. A gold-polonium -210 static eliminator is connected to an outlet end of the filter cartridge. Using this arrangement, the blow-off gun provides a particle free deionizing gas stream for clean room applications. While these blow-off guns are simple in construction and have proven commercially successful, they suffer from a number of practical difficulties. Although the cellulose cartridge has proven adequate for most filtering needs, it cannot typically remove particles as small as 0.02 .mu.m. Furthermore, in the prior blow-off gun system, ambient air would sometimes backflow into the static eliminator portion of the gun, thereby producing ozone, which damages the assembly. Finally, the serial cartridge/static eliminator arrangement of the prior gun results in a longer gun which is somewhat awkward for some users to operate.